Sultan is a referral to a Middle Eastern leader. Milton is further associating Satan with religious implications. Milton is implying the Muslim religion by comparing Satan to a sultan. The implications behind a sultan are perhaps violent. Historically Christians have repeatedly considered Muslims and most other religions different from their own savage or barbaric. The crusades were fought against the Muslims, and Milton compares Satan to a Sultan fighting against a Christian King. Satan and God fought in heaven, and the comparison of the sultan to Satan implies evil violence, as Muslims at the time were thought to be barbaric.